Biomedical Engineering Reference
In-Depth Information
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Figure 13.9
Isodose curves overlaid on the histology section shown in Figure 13.8.
The pale gray and darker gray curves denote a dose of 100 and 1000Gy, respectively.
The dose curves were calculated from the entire tissue section, which contained 852
of the YAS glass microspheres with a nominal activity of 2500 Bq/sphere at the
time of injection. Calculations indicated that localized regions received doses up to
8000Gy. The dose rapidly decreased at the normal tissue interface, outer curve. The
bar in the lower left corner represents 1 cm. (Adapted with permission from [18].
Copyright (2004) Elsevier Ltd.)
The isodose curves (showing lines of same dose) shown in Figure 13.9
were calculated from a 3D dose grid of the entire tissue section, which
contained 852 glass microspheres whose computed nominal activity
was 2500 Bq/microsphere at the time of infusion. The pale gray and
darker gray curves denote a dose of 100Gy (10 000 rad) and 1000Gy
(100 000 rad), respectively. The isodose curves in Figure 13.9 were
calculated using the activity of each microsphere, the decay constant for
90
Y, and the position of each microsphere within the tissue section (and
the two adjacent sections).
By counting the number of microspheres in the tumor and adjacent
normal tissue in the section in Figure 13.8, the ratio of the number of
microspheres in the tumor to normal tissue was found to be 16 : 1. In
addition, the isodose curves demonstrate that a major fraction of the
total dose was confined within the tumor, and the dose rapidly decreased
within about 4mm of reaching the tumor-normal tissue interface. Even
within the tumor itself, the dose is localized to small regions and can be
